Origin and de-icing of multiple generations of ice-cored moraines at Brúarjökull, Iceland |
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| Authors: | Anders Schomacker Kurt H Kjær |
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| Institution: | (e-mail: ), GeoBiosphere Science Centre, Department of Geology, Quaternary Sciences, Lund University, Sölvegatan 12, S-223 62 Lund, Sweden;Natural History Museum of Denmark, Geocenter Copenhagen, Geological Museum, University of Copenhagen, Øster Voldgade 5-7, DK-1350 Copenhagen K, Denmark |
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| Abstract: | Mature dead-ice has been overridden repeatedly by the Brúarjökull glacier, and multiple generations of ice-cored landforms occur, with ice cores originating at least from glacier surges in 1963-1964, 1890 and 1810. Ice-cores are located on the proximal slopes of end moraines and in the valleys, as ice-cored outwash and eskers, ice-cored drumlins and ice-cored moraine patches. This dictates that the sediments and internal architecture might not always match their end-products as de-icing progresses. Analysis of multi-temporal aerial photographs integrated with annual field measurements showed that the time required for a total de-icing in the forefield exceeds the duration of the quiescent phases between the surges, even in the current climate at the limit of permafrost. Quantifying melting progression suggests that complete de-icing of ice-cored landforms is not likely to occur. The mean de-icing rate is c. 9.8 cm/yr in 1890 ice-cored moraines, and c. 17.7 cm/yr in 1963-1964 ice-cored moraines. Backwasting of ice-cored slopes (c. 30 cm/yr) is the fastest melt process. Long-term downwasting rates derived from multi-temporal digital elevation models provide a superior insight into the impact of multiple glacier surges on the formation of dead-ice moraines in front of Brúarjökull. |
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